Ok, thanks to a thread on DANIWEB here's the solution to my problem - Hiren's BootCD (v15.1). Used miniXP to boot, and then run Fix HDD Controller app. This allowed Vista to boot far enough for me to run the driver cd that came with motherboard. Afterwards, life is good, Vista did not even complain about the new motherboard and licensing.

Windows can't find a boot device. I get around this problem by installing drivers for a third party SATA card before using the Windows install with the new mainboard; the SATA card is used for the first boot, after which it can be removed.

In this case, you have not done this, and Vista does not have the option for a repair install. You may need to reinstall Windows. If your old motherboard works at all, I suggest you reinstall it temporarily, buy a third party SATA card like a Rosewill, and install that and its drivers. Afterwards, you can follow my suggestions, update the chipset drivers, and reactivate Windows.

Regarding the Windows OEM license, you are allowed to replace the mainboard in the event of failure with a like unit and your actions are arguably within those guidelines.

Thanks for the feedback. Unfortunately I could not load drivers ahead of time as MOBO was unresponsive. I don't know who they use as a supplier, but this is 2nd time in this Vostro, and my son's died as well. The PCs were never really opened up, or taxed in any way (they were Vostros, not gaming PCs), so no real reason to their demise. 3 motherboards in 3 years should scream QC problem. I will have to see if Dell will send a Vista copy for me to reinstall; otherwise, looks like I will be upgrading to Win7 via builders copy on a new SSD...

Gigabyte is manufacturer of premium mainboards, so I'm surprised you're having this problem. I have a 220s I bought as a "barebones' in 2009 and it still works, although it hasn't been in use continuously.

Ok, thanks to a thread on DANIWEB here's the solution to my problem - Hiren's BootCD (v15.1). Used miniXP to boot, and then run Fix HDD Controller app. This allowed Vista to boot far enough for me to run the driver cd that came with motherboard. Afterwards, life is good, Vista did not even complain about the new motherboard and licensing.